pip list - Shows Installed Packages and Updates
Version 1.3 (2013-03-07) of pip saw the addition of "list", for listing currently installed packages and the latest version of those packages that is available. Nice.
$ pip list --outdated
google-api-python-client (Current: 1.0 Latest: 1.1)
pysolr (Current: 3.0.5 Latest: 3.0.6)
Move over freeze...